Yacht Stability
The angle of vanishing stability

 

As the boat heels more, RM decreases, until:

  • RM is zero.
  • The boat can invert!
The point of vanishing stability in a yacht.

 

Righting moment curve for flat water.

The above diagram tells us that if a boat heels far enough, it becomes stable upside down.

The point where this occurs is known as the Angle of Vanishing Stability or AVS.

Boats will not normally heel past their AVS. Obviously, the wind could not make this happen, the sails are under water, the only way for this to occur is for the force of the water to push the boat over.

A vessel which inverts will remain inverted until a wave rolls it past its angle of vanishing stability, then it will return to the correct orientation.

Link to angle of vanishing stability calculator.

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